The Evil Black Crystal, or Jakokusuishou (in Japanese: 邪黒水晶), was a diamond-ahaped black crystal from Sailor Moon R which grew with dark, negative energy. It was a precious mineral from the planet Nemesis that Death Phantom (Wiseman) used to try and destroy the planet Earth. The Black Moon Clan intends to let it grow enough to open the Black Gate and allow the world to be destroyed. The leaders of the Black Moon Clan, with the exception of Saphir, wore earrings made of this crystal.

In the anime, after the great battle in episode 88, Usagi and Chibiusa used the power of their two Silver Crystals to destroy the Evil Black Crystal.

The Black Poison Crystal

The Black Poison Crystal.

In the English dub, this material was called "Dark Crystal," in the TokyoPop manga translations it was called "Black Poison Crystal," and in the Kodansha manga it was "Malefic Black Crystal".

Black Gate

The Dark Gate

The Dark Gate, also known as the Black Gate.

The Black Gate, also known as the Dark Gate, is an interdimensional gateway created by the Evil Black Crystal that gives passaway between worlds signals the approaching forces of the Negamoon and the increasing power of the Doom Phantom (Wiseman). This door takes shape in the towing shiney hexagonal platform with the hexagram on the floor along with 6 black crystal pillars on it atop of the growing Evil Black Crystal that is planted and grew on any planet's ground surface and it creates a thunderous whirpool of the same name in the sky as a portal between dimensions throughout time and space.